The National Weather Service, Federal Emergency Management Agency and Army Corps of Engineers are constantly monitoring the Missouri River from Montana to Missouri as they anticipate historic flooding.

Click map to be redirected to Army Corps of Engineers flood maps and information.

The runoff from the Missouri River in May was 10.5 million acre feet of water — enough to cover 10.5 million acres of land one-foot-deep. (Each acre-foot equals 325,851 gallons.) That’s 3 million more than the historic runoff in 1995. Kevin Grody with the Corps of Engineers says the runoff was measured at 7.2 million acre feet in 1995, which was the most in 114 years of record keeping.

As far as how much more is coming this spring, Lynn Maximuk with the National Weather Service says that remains to be seen.

He says the Weather Service is watching more rain systems move in, and though there’s some indication they might move off to the east, it’s a wait-and-see situation. Montana and the Dakotas have gotten more than their average annual rainfall just over the past few weeks Record amounts of snowmelt will also lend to the flooding, Maximuk says. The snowmelt is about 140 percent of normal this year, some of which can be attributed to La Nina.

Maximuk says the National Weather Service is working with the Army Corps of Engineers and the Federal Emergency Management Agency to make sure everyone has the latest forecast and resources available.

Officials are urging communities all along the Missouri River — from Montana to south of St. Louis — to prepare for imminent flooding.

They say flooding will happen now through mid August … at the earliest.

AUDIO: Jessica Machetta reports [Mp3, 1:20 min.]